Though it lacks a lot of the buttons, tabs, and other flashy user interface elements commonly found in commercial mindmapping tools such as Mindjet MindManager or 3D Topicscape, FreeMind (free) is still a gold-standard mind mapping application. What makes it so powerful is its readily accessible controls and its cross-platform compatibility. In addition to a version that runs under Windows, the team that writes the program also supports Mac OS and Linux as well. There are even FreeMind-compatible mind mapping apps for both the iPhone and Android mobile platforms, because FreeMind sets the standard for compatibility.
FreeMind doesn't start you off with fancy wizards or step you through the process of building a mind map. At least, it doesn't do so within the confines of the program. A large and very helpful FAQ and good online documentation help fill in the gaps. But it does help if you've made a mind map before, because the concepts are essentially the same, even if the user interface looks a bit sparse.
That isn't to say the program doesn't allow you to customize its interface. To the contrary, mind maps don't have to remain grey blobs surrounded with underlined monochromatic text. You can insert small icons, add calendar entries or reminders to branches on the map, or see the timeline of revisions made to the map. FreeMind definitely lacks some of the aesthetic appeal that other products make part of their stock-in-trade, but the whole point is to make better plans or formulate ideas, not to have a pretty picture.
FreeMind's an excellent starting point for anyone who wants to try their hand at mind mapping, without expending a lot of effort learning a particular commercial product's interface quirks. And if you build something you want to later use in another product, virtually all mind mapping programs can import FreeMind's map files into their programs, so you won't have to reinvent the wheel.